Patent Application
20250015233
The present invention relates to a light emitting element and a light emitting device, and more particularly to a semiconductor light emitting element such as a light emitting diode (LED) and a light emitting device on which the semiconductor light emitting element is mounted.
A light emitting device on which a semiconductor light emitting element is mounted is used for various illumination or display devices, and the like. In particular, in recent years, the light emitting device on which the semiconductor light emitting element is mounted is required to be thinned in order to further achieve space saving.
For example, Japanese Patent Application Laid-Open No. 2010-219324 discloses a light emitting device that includes a mounting substrate having a base material and a wiring layer for external connection, and a light emitting element provided on a top surface of the mounting substrate and having both a first conductive type (negative) and a second conductive type (positive) electrodes.
Patent Literature 1: Japanese Patent Application Laid-Open No. 2010-219324
However, in the light emitting device that includes a mounting substrate having a base material and a wiring layer for external connection, and a light emitting element provided on a top surface of the mounting substrate and having both electrodes of a first conductive type (negative) and a second conductive type (positive), there is a problem in reliability, such as a risk of stress being concentrated between both electrodes, causing damage or deterioration of the semiconductor light emitting element.
The present invention has been made in view of the above points, and an object thereof is to provide a semiconductor light emitting element in which a luminous flux is improved when being used as a light emitting device, or a light emitting device in which reliability is improved and a luminous flux is improved while achieving thinning.
A semiconductor light emitting element according to Embodiment 1 of the present invention includes a flat plate-shaped translucent element substrate that has two main surfaces facing each other, a light emitting semiconductor layer configured to be formed on one main surface of the element substrate and in which an n-type semiconductor layer, a light emitting layer, and a p-type semiconductor layer are laminated, an n-electrode configured to be connected to the n-type semiconductor layer through at least one hole portion leading to the n-type semiconductor layer and provided on the p-type semiconductor layer to be electrically separated from the p-type semiconductor layer by an insulating film, a first element electrode configured to be electrically connected to the n-electrode and provided to extend in a first direction, and a second element electrode configured to be electrically connected to the p-type semiconductor layer and provided to extend in the first direction while being spaced apart from the first element electrode, in which a thickness of the element substrate is 100 μm or less.
Hereinafter, preferred embodiments of the present invention will be described, but may be appropriately modified and combined. In addition, in the following descriptions and the accompanying drawings, substantially the same or equivalent parts will be described with the same reference numerals. First, the description will be made for the semiconductor light emitting element and then for the light emitting device.
Embodiment 1 is a semiconductor light emitting element 10 used in a light emitting device 30 illustrated in
In
In the description of the semiconductor light emitting element 10, a direction where the light emitting semiconductor layer 12 is provided with respect to the element substrate 11 is referred to as an upward direction, and an opposite direction is referred to as a downward direction.
As illustrated in
As illustrated in
As the element substrate 11, a sapphire (Al2O3) single crystal is used. The bending strength of the sapphire single crystal is 690 MPa, and the sapphire single crystal has a high strength even in a case where the element substrate 11 is thinned. In the present embodiment, the thickness Tsub of the element substrate 11 is reduced to 100 μm to reduce the thickness of the entire semiconductor light emitting element 10. However, when the thickness is excessively small, the function as the framework is impaired, and thus the thickness is preferably in a range of 40 μm to 100 μm. For example, when the thickness is less than 40 μm, occurring defect such as a failure to light increase during the manufacturing or use of the semiconductor light emitting element 10 and the light emitting device 30. In addition, the framework strength is able to be improved when the thickness is more than 100 μm, but the light emitting device 30 is not able to be thinned. As the element substrate 11, an aluminum nitride (AlN) single crystal, a silicon carbide (SiC) single crystal, a gallium nitride (GaN) single crystal, or the like is also able to be used.
A rough surface layer or an anti-reflection coating (AR coating) that improves light extraction efficiency is able to be provided on the bottom surface 11B of the element substrate 11.
As illustrated in
The n-type semiconductor layer 13 of the light emitting semiconductor layer 12 has the same size as that of the element substrate 11 in a top view. In addition, the light emitting layer 14 and the p-type semiconductor layer 15 have an outer shape having one size smaller than the outer shape of the n-type semiconductor layer 13. That is, an exposed portion of the n-type semiconductor layer 13 surrounds the light emitting layer 14 and the p-type semiconductor layer 15 in a frame shape over the entire periphery.
In addition, as illustrated in
In the present embodiment, the number of the hole portions 12A is set to three, but may be one or two, or four or more. In addition, the hole portions 12A may be arranged in parallel in two rows.
The light emitting semiconductor layer 12 is made of a gallium nitride (GaN)-based compound semiconductor, and radiates blue light. The p-type semiconductor layer 15 or the n-type semiconductor layer 13 may include layers such as an un-doped layer, a strained-layer superlattice (SLS) layer, an electron blocking layer (EBL), a contact layer, or the like in addition to a layer doped with an impurity exhibiting a main conduction type.
(n-Electrode)
As illustrated in
The n-electrode 16 is formed by laminating titanium (Ti) and gold (Au) in this order. Hereinafter, the layers laminated in order will be referred to as Ti/Au. As the n-electrode 16, Ti/aluminum (Al), Ti/Al/platinum (Pt)/Au, Ti/Pt/Au, Ti/rhodium (Rh)/Au, or the like is also able to be used.
(p-Electrode)
As illustrated in
The first p-electrode 17A is formed by laminating nickel (Ni)/Au. As the first p-electrode 17A, indium tin oxide (ITO), Ni/Pt/Au, Ni/palladium (Pd)/Au, Ni/silver (Ag)/Pt/Au, Ni/Pt/Al/Pt/Au, or the like is also able to be used.
The second p-electrode 17B is formed by laminating Ti/Au. As the second p-electrode 17B, Ti/Al, Ti/Al/Pt/Au, Ti/Pt/Au, Ti/Rh/Au, or the like is also able to be used, similar to the n-electrode 16.
As illustrated in
The first insulating film 18A covers to protect and insulate the n-type semiconductor layer 13, the light emitting layer 14, and the p-type semiconductor layer 15. In addition, the first insulating film 18A covers to protect and insulate the side surface and the bottom surface of a part of the first p-electrode 17A in contact with the p-type semiconductor layer 15.
The second insulating film 18B covers to protect and insulate the n-electrode 16 and the second p-electrode 17B, except for a part of the first insulating film 18A.
As the insulating film 18, silicon dioxide (SiO2) is used. As the insulating film 18, an insulating metal oxide such as titanium dioxide (TiO2), hafnium oxide (HfO2), alumina (Al2O3), or the like is also able to be used.
The first element electrode 19 and the second element electrode 20 (hereinafter, both are referred to as an element electrode in a case where both are not distinguished) are provided on the top surface of the semiconductor light emitting element 10 as illustrated in
The first element electrode 19 (cathode) is connected to the n-type semiconductor layer 13 through the n-electrode 16, and the second element electrode 20 (anode) is connected to the p-type semiconductor layer 15 through the p-electrode 17. Therefore, by applying a voltage to the first element electrode 19 and the second element electrode 20, a current is able to be passed through the light emitting semiconductor layer 12, and the semiconductor light emitting element 10 is able to emit light.
As the element electrode, Ni/Au is used. As the element electrode, a highly conductive metal such as Ti/Au and Ti/Ni/Au is also able to be used.
Next, Comparative Example 1 will be described. Comparative Example 1 is a semiconductor light emitting element in which the thickness Tsub of the element substrate 11 according to Embodiment 1 is increased from 100 μm to 200 μm. The element substrate has the same configuration as that of the semiconductor light emitting element 10 according to Embodiment 1, except for the thickness.
The semiconductor light emitting element 10 according to Embodiment 1 and the semiconductor light emitting element according to Comparative Example 1 were bonded to a circuit substrate through a gold-tin bonding member, and a current was passed through each semiconductor light emitting element to compare the light output. As a result, in a case where the light output according to Comparative Example 1 was set to 100%, the light output according to Embodiment 1 was 98%. That is, the light output of the semiconductor light emitting element 10 according to Embodiment 1 is 2% lower than the light output of the semiconductor light emitting element according to Comparative Example 1.
The decrease in light output is due to a decrease in the area of the light output surface by thinning the element substrate 11. Therefore, the light output is further reduced as the thickness of the element substrate 11 is reduced to 70 μm and 40 μm. In addition, the mechanical strength of the semiconductor light emitting element 10 is also reduced at the same time.
Hereinbefore, the semiconductor light emitting element 10 according to Embodiment 1 is able to be thinned while reducing the light output and the mechanical strength in a single stage.
Next, a method of manufacturing a semiconductor light emitting element 10 according to Embodiment 1 will be described.
First, as the element substrate 11, an element substrate with a light emitting semiconductor layer 12 in which a gallium nitride-based n-type semiconductor layer 13, a light emitting layer 14, and a p-type semiconductor layer 15 are laminated on one surface of a sapphire single crystal substrate by epitaxial growth is prepared (SD1).
A resist mask is formed on a portion of the element substrate 11 with the light emitting semiconductor layer 12, which is a light emitting region, and etching is performed by reactive ion etching (RIE) until the n-type semiconductor layer 13 is exposed in a portion other than the resist mask. Thereafter, the resist mask is removed to form the light emitting region having the hole portion 12A (SD2).
A resist mask in which a portion to be the first p-electrode 17A is exposed is formed on the top surface of the p-type semiconductor layer 15 in the light emitting region, and Ni and Au are evaporated in this order as the first p-electrode 17A using an electron beam (EB) evaporation device. Thereafter, the resist mask is removed to form the first p-electrode 17A (SD3).
A SiO2 film is formed on the entire surface of the element substrate on which the first p-electrode 17A is formed, as an insulating film, by a sputtering device. Next, a resist mask is formed on a portion other than the formation of the bottom surface portion of the hole portion 12A and the second p-electrode 17B, and the insulating films on the bottom surface portion of the hole portion 12A and the second p-electrode 17B forming portion are etched and removed with a fluorine acid buffer solution to form the first insulating film 18A (SD4).
A resist mask is formed on a portion other than the portion to be the n-electrode 16 and the second p-electrode 17B, and Ti and Au are evaporated in this order as the n-electrode 16 and the second p-electrode 17B using the EB evaporation device.
Thereafter, the resist mask is removed to form the n-electrode 16 and the second p-electrode 17B (SD5).
A SiO2 film is formed on the entire surface of the element substrate on which the n-electrode 16 and the second p-electrode 17B are formed, as an insulating film, by a sputtering device. Next, a resist mask is formed on a portion other than a portion where the first element electrode 19 and the second element electrode 20 are formed, and the insulating films of the n-electrode 16 and the second p-electrode 17B forming portion are etched and removed with a fluorine acid buffer solution to form the second insulating film 18B (SD6).
A resist mask is formed on a portion other than a portion to be the first element electrode 19 and the second element electrode 20, and Ti and Au are evaporated in this order as the element electrodes using the EB evaporation device. Thereafter, the resist mask is removed to form the first element electrode 19 and the second element electrode 20 (SD7).
Next, the sapphire single crystal substrate of the element substrate on which the first element electrode 19 and the second element electrode 20 are formed is thinned to 100 μm using a grinding and polishing device to form the element substrate 11 (SD8). In order to thin the element substrate 11 to 70 μm, 40 μm, or the like, the amount of grinding and polishing of the sapphire single crystal substrate in this step may be increased. In addition, in order to form the semiconductor light emitting element according to Comparative Example 1 in which the element substrate 11 has the thickness of 200 μm, the amount of grinding and polishing may be reduced.
The laser scribing is performed along the contour line of each of the semiconductor light emitting elements 10 from the surface side (rear surface side) of the element substrate 11, and the element is individualized into one unit to form the semiconductor light emitting element 10 (SD9).
Next, a light emitting device 30 according to Embodiment 2 will be described.
Furthermore, in
In the description of the light emitting device 30, a direction where the semiconductor light emitting element 10 is provided with respect to the device substrate 31 is referred to as an upward direction, and an opposite direction is referred to as a downward direction. The XYZ coordinates are noted in each of the figures.
As illustrated in
As illustrated in
As the base body 32, an aluminum nitride (AlN)-based ceramic substrate having a thickness Tbase of 70 μm is used. An aluminum nitride (AlN)-based ceramic is an insulating ceramic having excellent thermal conductivity and bending strength, with a thermal conductivity of 180 to 220 W/mK and a bending strength of 300 to 350 MPa. From the viewpoint of making the light emitting device 30 thin, it is preferable that the thickness of the base body 32 is thin, and when the strength as the base body is taken into consideration, the thickness is preferably 30 μm to 120 μm. As the base body 32, a silicon nitride (Si3N4)-based ceramic or the like is also able to be used.
As illustrated in
The second wiring electrode 34 (anode) is provided on the other surface (surface in the −Y direction in
Each of the short sides of the first element placing region 33B of the first wiring electrode 33 and the second element placing region 34B of the second wiring electrode 34 is aligned with each other in a top view (XY plane). In other words, the outer edge obtained by combining the first element placing region 33B and the second element placing region 34B has a rectangular shape and has a size including the semiconductor light emitting element 10.
The first mounting electrode 37 (cathode) is provided on one surface (surface in the +X direction in
The second mounting electrode 38 (anode) is provided on the other surface (surface in the −X direction in
As described above, the first element placing region 33B of the first wiring electrode 33 and the second element placing region 34B of the second wiring electrode 34 are spaced apart from each other by a wiring electrode separation band 48 along the line segment LX2. That is, the element electrodes 19 and 20 are provided to be spaced apart from each other in an extension direction (Y axis direction) of a line segment LY2 orthogonal to the line segment LX2. In addition, the first mounting electrode 37 and the second mounting electrode 38 are spaced apart from each other by a mounting electrode separation band 47 along the line segment LY2 orthogonal to the wiring electrode separation band 48. That is, the first mounting electrode 37 and the second mounting electrode 38 are provided to be spaced apart from each other in the extension direction (X axis direction) of the line segment LX2. In this manner, by making the wiring electrode separation band 48 of the element placing regions 33B and 34B and the mounting electrode separation band 47 of the mounting electrodes 37 and 38 orthogonal to each other, when the semiconductor light emitting element 10 is bonded and the light emitting device 30 is mounted on the circuit substrate, it is possible to prevent the device substrate 31 from being bent even when the device substrate 31 is made thin.
The first conduction via 35 (cathode) penetrates the base body 32 between the first land 33A of the first wiring electrode 33 and the first mounting electrode 37 up and down, and electrically connects both.
The second conduction via 36 (anode) penetrates the base body 32 between the second land 34A of the second wiring electrode 34 and the second mounting electrode 38 up and down, and electrically connects both.
Since the surfaces of the wiring electrodes 33 and 34 and the mounting electrodes 37 and 38 to which the conduction vias 35 and 36 are connected have irregularities, and the smoothness of the electrode surface is impaired, the conduction vias 35 and 36 are provided in portions other than the first element placing region 33B of the first wiring electrode 33 and the second element placing region 34B of the second wiring electrode 34.
The first wiring electrode 33, the second wiring electrode 34, the first mounting electrode 37, the second mounting electrode 38, the first conduction via 35, and the second conduction via 36 are made of a metal having copper (Cu) as a main component. In addition, the wiring electrode and the mounting electrode are plated with a Ni/Au layer on the surface thereof. As the main body metal of the wiring electrode, the mounting electrode, and the conduction via, tungsten (W) or the like is also able to be used.
The semiconductor light emitting element 10 is a flip chip including the first element electrode 19 and the second element electrode 20 having substantially the same size and rectangular shapes on a surface facing the element substrate 11, which is the light output surface. In addition, in the semiconductor light emitting element 10, each of the first element electrode 19 and the second element electrode 20, and each of the first element placing region 33B and the second element placing region 34B are connected to each other through the bonding member 41. The semiconductor light emitting element 10 including such element electrodes 19 and 20 has excellent self-alignment properties to the element placing regions 33B and 34B of the device substrate 31, and has low residual stress of the bonding. That is, even when the element substrate 11 or the device substrate 31 is thin, the bonding is able to be performed with good yield. The size of the semiconductor light emitting element 10 used in the present embodiment is a quadrangular shape having a side of approximately 1000 μm and a thickness of approximately 100 μm (thickness of the semiconductor light emitting element 10≈thickness of the element substrate 11). In consideration of ease of handling in the manufacturing step of the semiconductor light emitting element 10 having a thin thickness, it is preferable that the length of one side (line segment LX and line segment LY) is 600 μm to 1600 μm.
As illustrated in
Although a Zener diode is used as the protective element 39 of the present embodiment, a capacitor, a varistor, or the like is also able to be used as the protective element 39, in addition to the Zener diode.
As the bonding member 41, a gold-tin (Au-20 wt % Sn) alloy is used. A gold-tin cream solder is used for forming the gold-tin alloy. The flux contained in the gold-tin cream solder evaporates when the semiconductor light emitting element 10 and the protective element 39 are bonded to the device substrate 31. The surfaces of the element placing regions 33B and 34B to which the semiconductor light emitting element 10 is bonded are smooth, and the bonding members 41 are formed with a uniform thickness in a region where the element electrodes 19 and 20 of the semiconductor light emitting element 10 overlap the element placing regions 33B and 34B. As a result, the stress during the bonding applied to the thin semiconductor light emitting element 10 is able to be reduced, and the damage to the semiconductor light emitting element 10 is able to be prevented.
The phosphor plate 43 as a wavelength conversion member has a flat plate shape substantially the same size as the light output surface of the semiconductor light emitting element 10 in a top view. In addition, the phosphor plate 43 is a ceramic phosphor in which cerium-activated yttrium aluminum garnet (YAG: Ce) phosphor particles are contained in an alumina base material. As illustrated in
The phosphor plate 43 may be smaller or larger than the light output surface of the semiconductor light emitting element 10. In addition, an uneven structure for reducing reflectivity, a translucent protective film for protecting the surface, a dielectric multi-layer film for controlling the orientation characteristics, or the like may be provided on the surface of the light incident surface (bottom surface) or the light output surface (top surface) of the phosphor plate 43. In addition, a reflective dielectric multi-layer film or a white ceramic film may be provided on the side surface.
As a base material of the phosphor plate 43, an inorganic material such as a translucent ceramic or glass, a translucent resin material, or the like is able to be used. In addition, the light conversion particles are not limited to the cerium-activated yttrium aluminum garnet (YAG: Ce) phosphor, cerium-activated lutetium aluminum garnet (LuAG: Ce) phosphor, europium and/or cerium-activated orthosilicate ((Ba, Sr, Ca) SiO4: Eu, Ce) phosphor, cerium-activated terbium aluminum garnet (TAG: Ce), europium-activated α-sialon phosphor (α-SiAlON: Eu), europium-activated β-sialon phosphor (β-SiAlON: Eu), manganese-activated potassium fluorosilicate (KFS: Mn), or the like is able to be used, and different types of the light conversion particles are able to be appropriately selected and used depending on the wavelength of the excitation light, a desired color tone, and the like.
As illustrated in
As the coating member 44, a white resin obtained by dispersing reflective titanium oxide (TiO2) fine particles in a medium of translucent silicone resin is used. As a translucent medium, an epoxy resin, an acrylic resin, a polycarbonate resin, a polystyrene resin, or the like is also able to be used. In addition, as the reflective fine particles, mixed ceramic particles of alumina (Al2O3) and zirconia (ZrO2) is also able to be used.
In the light emitting device 30 according to Embodiment 2, each of the first mounting electrode 37 and the second mounting electrode 38 is mounted on the circuit substrate through soldering. The wiring electrode separation band 48 between the first element placing region 33B and the second element placing region 34B of the light emitting device 30 is orthogonal to the mounting electrode separation band 47 between the first mounting electrode 37 and the second mounting electrode 38. Therefore, in the mounting of the light emitting device 30 on the circuit substrate, the stress of bending the linear portion in which the three hole portions 12A of the semiconductor light emitting element 10 are arranged is suppressed. As a result, even when the element substrate 11 and the device substrate 31 are thin, it is possible to prevent a malfunction such as a short-circuit of the light emitting device 30, and improve the reliability of the light emitting device 30.
Next, a light emitting device according to Comparative Example 2 will be described. The light emitting device according to Comparative Example 2 is a light emitting device in which the thickness of the element substrate 11 of the semiconductor light emitting element 10 of the light emitting device 30 according to Embodiment 2 is changed from 100 μm to 200 μm, and the other configurations are the same as those of
The light emitting device 30 according to Embodiment 2 and the light emitting device according to Comparative Example 2 were bonded to a circuit substrate by soldering, and a current was passed through each light emitting device to compare the light output. As a result, in a case where the light output according to Comparative Example 2 was set to 100%, the light output according to Embodiment 2 was 108%. That is, the light output of the light emitting device 30 according to Embodiment 2 was increased by 8%. This is considered to be because a contact area between the element substrate 11 of the semiconductor light emitting element 10 and the coating member 44 is reduced. Similarly, when the element substrate 11 is thinned to 70 μm and 40 μm, the light output is increased. In this manner, the semiconductor light emitting element 10 according to Embodiment 1 used in the light emitting device 30 according to Embodiment 2 tends to decrease the light output in the single unit, but by using the light emitting device 30 according to Embodiment 2, the light emitting device 30 has high light output (luminous flux) characteristics. In addition, by thinning the light emitting device 30, it is possible to suppress light leakage from the side surface of the light emitting device 30 and to increase the light output from the light output surface of the light emitting device 30 (top surface of the phosphor plate 43).
Hereinbefore, according to the present invention, it is possible to provide the semiconductor light emitting element 10 in which a luminous flux is improved when used as the light emitting device 30, or the light emitting device 30 in which the reliability is improved and the luminous flux is improved while achieving thinning.
Hereinafter, a method of manufacturing a light emitting device 30 according to Embodiment 2 will be described in detail with reference to the flowchart and the drawings.
As the device substrate 31, a substrate in which the first wiring electrode 33, the second wiring electrode 34, the first conduction via 35, the second conduction via 36, the first mounting electrode 37, and the second mounting electrode 38 were provided on the base body 32 and a plurality of device substrates 31 for the light emitting device was integrated with each other was prepared (
A gold-tin (Au—Sn) cream solder as the bonding member 41 was applied onto the first wiring electrode 33 and the second wiring electrode 34 on which the semiconductor light emitting element 10 and the protective element 39 were mounted. Next, the semiconductor light emitting element 10 and the protective element 39 were placed on the gold-tin cream solder.
Next, the semiconductor light emitting element 10 was heated to 300° C. in a reflow furnace to melt and solidify the gold-tin cream solder, and the semiconductor light emitting element 10 was mounted on the first wiring electrode 33 and the second wiring electrode 34. At the same time, the protective element 39 was also mounted on the second wiring electrode 34. Thereafter, the upper electrode of the protective element 39 and the first wiring electrode 33 were electrically connected to each other by a wire 40 (
A silicone resin, which was a translucent adhesive agent, was applied to the top surface of the semiconductor light emitting element 10 as the adhesive member 42. Next, the phosphor plate 43 was placed on the semiconductor light emitting element 10. The adhesive member 42 was heated at 170° C. for 10 minutes to temporarily cure the silicone resin, and the phosphor plate 43 was adhered onto the semiconductor light emitting element 10 (
A frame body 45 was formed on the outer peripheral edge of the plurality of device substrates 31. The inside of the frame body 45 was filled with the coating member 44 made of silicone resin mixed with titanium oxide particles up to a height in contact with the outer peripheral edge of the top surface of the phosphor plate 43. Thereafter, the silicone resin was cured by heating at 100° C. for 30 minutes and at 150° C. for 1 hour. At this time, the adhesive member 42 was also main-cured (
The light emitting device 30 was cut for each unit with a dicing blade 46 and individualized. Through the above steps, the light emitting device 30 was manufactured (
Next, a light emitting device 50 according to Embodiment 3 will be described. Description of the same configuration as that of the light emitting device 30 according to Embodiment 2 of the present invention will be omitted as appropriate.
As illustrated in
In this manner, by driving the two light emitting devices 30 in parallel, the semiconductor light emitting elements 10 included in each of the light emitting devices 30 are able to be individually turned on. Therefore, for example, by making the wavelength conversion characteristics of the phosphor plate 43 included in the light emitting device 30 different from each other, it is possible to emit light of a plurality of colors with one light emitting device.
Next, a modification example of the light emitting device 50 according to Embodiment 3 is that, as illustrated in
In the present embodiment, the number of the light emitting devices 30 included in the plurality of unit type light emitting device 50 is set to two, but may be three or more. In addition, as illustrated in
As described above, according to the present invention, it is possible to provide the semiconductor light emitting element or the light emitting device in which the reliability is improved and the luminous flux is improved while achieving thinning.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-109538 | Jul 2023 | JP | national |
